Many pharmaceutical products are supplied in glass vials which have a closure which can be penetrated by a syringe so as to add or subtract material from the container. For example, often times, medicines are supplied in dry form inside a vial having a rubber closure or stopper. Liquid such as deionized water is added to the vial to dissolve or suspend the solid material. Sometimes, serum and other medicines are freeze dried in the vial and ar then reconstituted in the vial.
When an ordinary container and closure is used to dispense medicines which have been reconstituted, several problems are created. Normally when a liquid is added to a powder in a vial there is an increased pressure in the container and syringe due to the change in volume. This pressure tends to force a discharge of the liquid through an opening formed by the closure puncture and the hypodermic needle point, either when the needle is withdrawn or later when a needle is inserted to withdraw some of the contents.
Another difficulty arises when the powders and the newly formed liquids experience aerosoling. This phenomenon occurs when small particles or droplets, either powder or in the liquid state, become airborne during the turbulence caused from the pressure released during withdrawal or insertion of the needle into the container. Thus, these airborne particles escape from the container and may contact the health care worker.
Normally, the above described problems are inconvenient but do not create a major cause for concern. However, advances in modern medicine have made the aerosoling problem and others as described above much more serious. Specifically, during the treatment of cancer, chemotherapy drugs are packaged in glass vials in a freeze dried form and are thereafter reconstituted at the time when treatment is beginning. Various quantities of the reconstituted liquid are withdrawn over a period of time using syringes. Because cancer treating drugs are often times powerful, sometimes causing retardation or stoppage of all cell growth, it is obviously an advantage to avoid having unnecessary contact. Every effort is made to avoid contact by the preparer and dispenser of chemotherapy drugs. Not only cancer treating materials are of concern. As AIDS and AIDS related diseases are treated, drugs which are used may not be safe for universal contact. Antibiotics and cloning drugs also need to be carefully monitored.
Accordingly, it is an object of the this invention to provide a cap assembly for use with a closed container having a closure which captures the immediate atmosphere generated by the addition of fluids to the contents of the vial via a syringe. It would be of great advantage if a device could be designed which would keep chemicals from leaving containers and which would capture and release pressure generated during the use of syringes in association with those containers. Other objects will appear hereinafter.